1. Field of the Invention
The present invention relates to a perspective projection image creation system including an omnidirectional vision sensor, a perspective projection image creation method, a perspective projection image creation program and a recoding medium storing the perspective projection image creation program.
2. Description of the Related Art
In recent years, studies have been actively carried out for an image display system including a camera and a monitor installed in a mobile body, such as a car, so as to display an image in a driver's blind spot on the monitor. A representative example of such an image display system includes a rearview monitor installed in a car so as to reduce the burden imposed on a driver, for example, when the driver parks the car.
However, in a conventional image display system, for example, an angle of view is narrow right behind the car, so that information displayed on a monitor is limited. Therefore, there is a need for an image display system including a camera which has a wider angle of view and can obtain more accurate information on a positional relationship between a car and obstacles, in order to further reduce the driver's burden.
Moreover, in a conventional image display system such as an image display system including a rearview monitor, an image captured by a camera is displayed on a display screen of the monitor substantially without being processed, so that a range covered by the displayed image is limited to a specific field of view, for example, in an area behind a car. With the conventional image display system, a driver of the car can observe obstacles located directly behind the car or the driver can recognize how far the car can be backed up. However, the driver cannot obtain information on the surroundings except in the area directly behind the car, e.g., the driver cannot recognize a positional relationship between the car and obstacles or the like, such as lines indicating a parking space or adjacent cars parked next to the driver's car.
Therefore, the driver of the car is required to drive or park the car by making good use of their driving experience while checking the image displayed on the monitor or looking in rearview and/or side mirrors. This imposes a considerable burden on an inexperienced driver and prevents the driver's safety driving.
In view of the above-described circumstances, there is a need for an image display system used as a driving assistance system which provides a driver of a car with accurate positional information on the surroundings around the car, for example, in a car park. Japanese Patent Application No. 2000-31260 discloses a mobile body surround surveillance apparatus which includes an omnidirectional vision sensor using a hyperboloidal mirror installed at a prescribed position in a car such that a field of view of the omnidirectional sensor is directed downward to the ground plane, i.e., the omnidirectional sensor captures an image of the ground as if the ground is viewed from directly above. That is, the mobile body surround surveillance apparatus produces a bird's eye view of the ground based on a perspective projection image obtained by the omnidirectional vision sensor, thereby providing two-dimensional information on a position of a mobile body, such as a car, with respect to the ground plane.
However, such a conventional mobile body surround surveillance apparatus disclosed in Japanese Patent Application No. 2000-31260 produces the bird's eye view using the perspective projection image as if the car, which does not actually exist on the ground plane, does exist on the ground plane, so that the bird's eye view of the car is significantly distorted, making it difficult to judge a positional relationship between the car and the ground plane, and therefore obstacles located thereon.
Japanese Patent Application No. 2000-31260 also discloses a configuration which enables the positional relationship between the car and the ground plane to be accurate and obvious in the bird's eye view by combining the distorted image of the car on the bird's eye view with an image showing the car as if the car is viewed from above. However, Japanese Patent Application No. 2000-31260 does not give detailed description of a method for producing such a combined image, which is, in fact, produced by a driver of the car repeating adjustments of a display screen through trial-and-error while viewing the display screen. Therefore, it is not easy for the driver to make slight changes, such as zooming-in or zooming-out, to the displayed image. Furthermore, no mechanism is provided to enable the driver to recognize an actual distance from the car to obstacles, lines indicating a parking space, etc.